1. Field of the Invention
The present invention relates to a wavelength division multiplexed-passive optical network, and more particularly to a wavelength division multiplexed-passive optical network having a bus structure capable of connecting one central office to a plurality of remote nodes via a single optical fiber.
2. Description of the Related Art
In general, a wavelength division multiplexed-passive optical network (WDM-PON) provides specific wavelengths to subscribers in order to ensure communication security and enhance communication services required by the subscribers. In addition, the WDM-PON can easily adapt new subscribers by simply increasing the number of dedicated wavelengths dedicated to the new subscribers.
Referring to FIG. 1, a conventional WDM-PON 100 has a star structure including a central office (CO) 10 connected to a remote node (RN) 20 through a feeder fiber 1 and the remote node 20 connected to a plurality of subscriber units 30 through distribution fibers by using a multiplexer/demultiplexer 21. In this regard, the multiplexer/demultiplexer 21 mainly uses an array waveguide grating (AWG) for the subscriber units.
As shown in FIG. 1, downstream signals multiplexed by a multiplexer/demultiplexer 11 of the central office are transferred to the remote node 20 through the feeder fiber 1 and demultiplexed by the multiplexer/demultiplexer 21 positioned at the remote node 20. Then, the downstream signals are transferred to each of subscriber units 31 and 32 through corresponding distribution fibers 2. Upstream signals outputted from the subscriber units 31 and 32 are transferred to the remote node 20. The upstream signals of subscribers, which are inputted to the multiplexer/demultiplexer 21 positioned at the remote node 20, are multiplexed so as to be transferred to the central office 10.
The conventional WDM-PON 100 mainly employs an expensive array waveguide grating as the multiplexer/demultiplexer 21, and a passive optical network (PON) having the structure described above is suitable for a plurality of subscribers in major cities. However, the PON having such a structure is not economical in areas outside the major cities, which have a smaller number of subscribers.